1. Field of the Invention
This invention relates to a hydraulic cold-extrusion press comprising a frame and a pressurized fluid drive where an exchangeable die part is provided on a platen which is capable of being moved towards and away from a stationary table, another exchangeable die part is mounted on a stationary table, the die parts when moved up against each other form a housing-shaped closed die, piston/cylinder means provided on the frame engage the platen for its two-way movement, an ejector capable of being extended and retracted by piston/cylinder means provided on the frame is allied to the table, working piston/cylinder means are provided on the frame to exert pressure for extrusion, and a controlled main valve is provided ahead of the working piston/cylinder means, the piston/cylinder means engaging the platen closing the die without deforming the workpiece contained in it and keeping it closed for the cold extrusion operation, and an exchangeable extrusion mandrel penetrating into the housing-shaped die to effect cold extrusion of the workpiece being acted upon by the working piston/cylinder means.
2. Description of the Prior Art
A prior-art (German Pat. No. 21 41 980) cold-extrusion press is of the multi-step type with respect to the die. The piston/cylinder means engaging the platen also serve as working piston/cylinder means and close the die with the workpieces contained in the die being subjected to cold extrusion in the process. The main valve is opened for the closure of the die and the cold extrusion operation and closed when the die is closed and, consequently, cold extrusion has been completed. A drawback of this prior press is in the fact that the workpiece is formed in several steps. Neither is it possible in this manner to produce workpieces of the type where the material of the slug of metal is required to flow into cavities at right angles to the extrusion pressure.
It is also known in the prior art (German Preliminary Pat. No. 24 19 167) that a split die is closed without deformation of the workpiece contained in it and kept closed for cold extrusion and that an extrusion mandrel penetrating into the housing-shaped die is provided to effect cold extrusion. This arrangement permits precise workpieces to be produced with minimum rework by means of only one cold extrusion operation. Also, the material of the slug will flow into intricate cavities at right angles to the extrusion pressure. This die and the extrusion mandrel are operated by means of a hydraulic press, no details being given about the arrangement of the hydraulic press.